This invention relates to registration controllers for web processing apparatus, and in particular to such registration controllers which do not have to be readjusted for webs having different reflectivities.
In the past there have been available many different types of photo responsive systems for sensing the registration of certain appropriately placed marks on webs being processed. Generally, however, a change in the type of web required a change in the placement of a scanner with respect to the web. Thus, for instance, a change from plain paper to highly reflective foil required the operator to move the scanner from a position perpendicular to the particular web under inspection to a position at an angle of about 22 degrees thereto. Then, when the foil run was completed and the operator was required to change back to plain paper, the scanner had to be adjusted again, back to the perpendicular position. This scanner adjustment procedure caused substantial down time because of the difficulty caused by the many fine adjustments required.
In addition, such registration systems generally included a light source located at or very near the web itself. Photo responsive registration systems having this characteristic are rated safe for use only in non-explosive environments. A need exists for similar photo responsive registration systems which can be safely used in any environment.
This invention relates to improvements to the apparatus described above and to solutions to some of the problems raised thereby.